1. Field of the Invention
The present invention generally relates to a display device and, more particularly, to a display device capable of modulating the brightness of a backlight module thereof according to the intensity of ambient light.
2. Description of Related Art
Along with the development of technologies, flat panel displays, such as liquid crystal display (LCD), plasma display panel (PDP), and so on, have gradually replaced cathode ray tube (CRT) as the mainstream of display products. Presently, thin film transistor liquid crystal display (TFT-LCD) panel is the most commonly-adopted LCD panel.
LCD TV has become commonly accepted along with the increase of its size and the reduction of its price. Meanwhile, the demand to the performance and quality of LCD TV has been increasing, wherein contrast ratio is one of the most important characteristics. Since the contrast ratio of an image displayed by a LCD is affected by the ambient light, brightness of the back light in the LCD should be adjusted according to the intensity of ambient light in order to improve the contrast ratio and to reduce the power consumption of the LCD. In particular, the reduction of power consumption has become one of the most important subjects in today's technology development due to the increasing energy price and global warming.
A display device having photo-sensors for detecting the intensity of ambient light is disclosed in U.S. Pat. No. 6,710,318. FIG. 1 schematically illustrates the conventional display device having photo-sensors. Referring to FIG. 1, the display device 100 includes a display panel 110 and two photo-sensors 120. The photo-sensors 120 of the display device 100 are close to the display panel 110. The photo-sensors 120 are used for detecting the intensity of ambient light.
Since the photo-current of the photo-sensors 120 is generated in accordance with the intensity of received light, the intensity of the back light in the display device can be adjusted according to the photo-current. However, the photo-sensors 120 are usually more sensitive to light with specific intensities. Namely, the photo-sensors 120 have limited illumination sensing capability. For example, the photo-sensors 120 which has high sensitivity to light with low intensity always outputs a maximum photo-current or a saturated photo-current when the photo-sensors 120 are irradiated by light with medium intensity or light with high intensity, which means the photo-sensors 120 cannot correctly distinguish lights of medium to high intensities. So, the photo-sensors 120 which has high sensitivity to light with high intensity cannot correctly distinguish lights of medium to low intensities because the photo-current produced by the photo-sensors 120 is too small and is easily distorted by noises.
However, in a real circumstance, the intensity of ambient light changes drastically along with the changes of sunlight or different light emitting source provided by a user. Thereby, the contrast ratio of the display device 100 can be enhanced and the power consumption thereof can be reduced if the photo-sensors 120 can detect lights of different intensities precisely.